This invention relates, in general, to thyristors and, more particularly, to bidirectional two-terminal thyristors.
In general, thyristors are a family of four layer PNPN type devices that function as switches in power control applications. Thyristors are available as unidirectional and bidirectional devices. A power dissipation of a unidirectional thyristor may be lowered by narrowing a width of its wide-base region. The wide-base region may be narrowed by, for example, fabricating the unidirectional thyristor in a thin semiconductor substrate.
The narrower wide-base region provides a lower forward voltage drop across the unidirectional thyristor; thereby permitting an increase in its current carrying capability while allowing an acceptable power dissipation. Lowering the power dissipation of a bidirectional thyristor by using the thin semiconductor substrate is unfeasible because of the fragility of the semiconductor substrate for practical thicknesses. Accordingly, it would be advantageous to have a method for decreasing a forward voltage drop, commonly referred to as an on-state voltage drop, without compromising a structural integrity of the semiconductor substrate.